WEST LAFAYETTE, Ind. — One of the best ways to keep cattle
healthy and gaining pounds in hot weather is to control flies, a Purdue
Extension beef specialist said.
Heavy populations of flies can cause stress in cattle herds
and spread disease. Both stress and disease can reduce milk production and calf
“We’re into June, so producers should start looking for the
fly populations, and they need to knock those fly populations down soon,” Ron
There are two main fly species that Indiana cattle producers
need to worry about — the horn fly and the face fly.
The horn fly is a small, blood-sucking insect that feeds
mainly on the backs, sides, shoulders and underlines of cattle. They reduce
weight gain and make animals more prone to stay in the shade instead of going
out in the sun to graze, Lemenager said.
Horn flies are usually easier to control than face flies
because they don’t travel far.
“Horn flies typically stay with the animal, only leaving to
deposit eggs in manure,” Lemenager said.
Face flies are known to travel more from animal to animal
and from farm to farm.
“If neighbors aren’t controlling face fly populations, you
will get more flies bothering your herd,” Lemenager said.
Non-biting face flies are about twice the size of horn flies
and similar in size to houseflies.
Face flies feed on the secretions around the eyes and heads
of cattle. In addition to irritating the skin, they can spread pink eye,
Pink eye, also known as conjunctivitis, can rapidly spread
through a herd and reduce weight gain and milk production. But the face fly
spreading the Moraxella family of bacteria isn’t the only contributing factor of
Lemenager said pink eye requires three basic elements: flies
transmitting the bacteria, ultraviolet radiation from the sun and mechanical
injury to the eye. Dust, seed heads, pollen, fescue leaves or sharp points on
grass can all irritate an animal’s eye.
So in addition to fly control, farmers should knock down or
clip pastures before turning the herd into a new pasture or paddock.
Producers have a few options for controlling flies in their
herds. One option, a newer technology, is to use insecticide-impregnated ear
The tags contain the pyrethroid or organophosphate class of
insecticides and are effective in reducing face fly populations for several
Lemenager recommended rotating pyrethroid and
organophosphate products so flies don’t build up resistance.
Farmers also can control fly populations for several weeks
by using insecticides in dust bags, oilers, pour-ons and sprays. Feed-through
larvacides in a mineral supplement form also have efficacy in disrupting fly